(Applicant's Abstract) Appropriate models are crucial to the study of early lung development, the pathobiology of developmental processes and investigation of the factors regulating the developmental events. The ability to manipulate suspected regulatory components of development is essential to productive studies. The primary explant culture model of fetal lung has been well characterized and mimics many maturational events characteristic of fetal lung in vivo. The Tissue Culture Core Laboratory has extensive experience in primary culture of lung tissue and cells, utilizing both explant culture and the recently developed and characterized monolayer culture of differentiated alveolar epithelial cells. The latter model of type II cell differentiation in vitro has been extensively characterized and provides an easily manipulated model of differentiation. These cells, as well as fibroblasts and pulmonary cell lines are useful for transfection, transduction and other approaches to study altered gene expression. This system of epithelial cell differentiation in vitro will be extended to the fetal rat and mouse lung as required for proposed studies with rodent lung; the mouse model has obvious advantages, particularly the availability of numerous genetic variants. The lung bud organ culture model provides an early model of mesenchymal, epithelial and vascular cell development, as well as cell type interaction during branching and epithelial cell maturation. The specific aims of this Core are to support the research goals of Projects I-V as follows: 1. Provide cultured tissue for all Projects: a) Prepare and maintain primary explant cultures of fetal lung as requested (human, rat, mouse); b) Prepare enriched isolated cell populations (type II cells, both undifferentiated and differentiated; fibroblasts) from fetal human, rat, mouse lung for short term study; c) Prepare mouse lung bud cultures as needed; d) Provide monolayer cultures of pulmonary and other cell lines when requested. 2. To maintain a bank of necropsy lung samples of interest (sectioned slides, frozen tissue, etc.), including those from infants with BP-D, SP-B deficiency and normal donor lung from transplants and to provide them to all Projects upon request. The Core will also assist distribution of sheep and rat tissues and slides as needed. 3. Co-ordinate and organize integrated use of culture setups between Projects, to maximize efficient use of tissue resources and facilitate data correlation and exchange. 4. Fix and embed tissue samples for microscopy (light, electron) as needed. 5. Provide training for fellows and technical staff in primary culture models, both manipulation technical issues as well as scientific expertise in experimental application of the models to solve problems. 6. Provide an interactive focal center for exchange of ideas, and integration of hypotheses and experimental findings by various SCOR investigators.